Most liquid crystal display (LCD) devices are passive devices in which images are displayed by controlling an amount of light input from an external light source. Thus, a separate light source (for example, backlight module) is generally employed for illuminating an LCD.
Generally, backlight modules can be classified into an edge type or a direct type based upon the arrangement of lamps within the device. The edge type backlight module has a lamp unit arranged at a side portion of a light guiding plate for guiding light. These edge type backlight modules are commonly employed in small-sized LCDs due to their lightweight, miniature and low electric consumption.
One kind of display device is illustrated in FIG. 1. The display device 100 includes a first frame 102, a backlight module 110, a display panel 160, and a second frame 104 stacked upon each other in that order. The first frame 102 is engaged with the second frame 104 so as to hold the display device 100 together.
The backlight module 110 includes a light guide plate 120, a reflective sheet 130, a light source device 140, and an optical correcting unit 150. The reflective sheet 130 is attached to the first frame 102. The light guide plate 120 includes a light incident surface 121, a light emitting surface 122 connected with the light incident surface 121, and a bottom surface 123 facing an opposite direction of the light emitting surface 122. The light guide plate 120 is located between the reflective sheet 130 and the optical correcting unit 150, with the bottom surface 123 adjacent to the reflective sheet 130 and the light emitting surface 122 adjacent to the optical correcting unit 150. The optical correcting unit 150 includes a diffusion sheet 151, a first brightness enhancement sheet 152, a second brightness enhancement sheet 153, and a hood light sheet 154, stacked in that order. The light guide plate 120, the reflective sheet 130, and the optical correcting unit 150 are all made of plastic material. The light source device 140 is located at one end of the light incident surface 121 of the light guide plate 120. The light source device 140 includes a light source 141 and a reflector 142 partially surrounding the light source 141. The reflector is configured for focusing light produced by the light source 141 so that most of the light is emitted to the light guide plate 120, and to increase utilization efficiency of light energy.
However, the backlight module 110 needs the reflector 142 for light focusing, and the cost of the reflector 142 is high and extra, thus, giving a high cost on the overall unit. On the other hand, some light may disappear through an edge of the reflector 142, thereby causing light energy loss. Furthermore, the light source 141 produces a great deal of heat that accumulates inside the display device 100. This causes plastic elements, for example, the light guide plate 120, the reflective sheet 130, and the optical correcting unit 150, to overheat and deform, resulting a lower display quality of the display device 100. Therefore, heat dissipation of the display device 100 is usually a hard nut to crack.
Therefore, a new display device is desired in order to overcome the above-described shortcomings.